Never means at no time in the past or at no time in the future.
I have never lost the weight I put on in my teens.
我在十几岁时增加的体重从没减下去过。
Never had he been so free of worry.
他从没这样无忧无虑过。
That was a mistake. We'll never do it again.
那是个错误,我们永远不会再犯了。
Never means 'not in any circumstances at all'.
I would never do anything to hurt him.
我决不会做任何伤害他的事情。
Divorce is never easy for children.
父母离婚对孩子来说绝不是件轻松的事情。
Never is used to refer to the past and means 'not'.
He never achieved anything.
他一事无成。
I never knew him.
我不认识他。
never ever
Never ever is an emphatic way of saying 'never'.
I never, ever sit around thinking, 'What shall I do next?'
我从来就不会闲坐着想:“我下一步该做什么?”